Plasma processing device and method for preventing plasma leakage

Abstract

The invention provides a plasma processing device and a method for preventing plasma leakage, and the device comprises a reaction cavity which is internally provided with a pedestal used for bearing a wafer, and the pedestal is electrically connected with a first non-constant voltage power supply; the restraint ring is arranged on the periphery of the base in a surrounding mode, and the space in the reaction cavity is divided into a plasma processing area and an exhaust area communicated with an external vacuumizing device; the restraint ring is electrically connected with the second non-constant-voltage power supply; plasma is prevented from entering the exhaust area through the restraint ring. Even under the condition that the plasma density in the reaction cavity is high, the plasma leakage can be avoided, and the condition that the exhaust flow guide of the restraint ring meets the process requirement is ensured.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a plasma processing apparatus and a method for preventing plasma leakage. Background Technology

[0002] During plasma etching, various process gases are injected into the reaction chamber of the plasma processing unit and excited into plasma under the influence of the radio frequency electric field within the chamber. The reaction between the plasma and the wafer produces by-products, which need to be promptly removed from the reaction chamber to ensure the smooth progress of the etching reaction. Currently, a flowing gas reaction chamber is used, where reactive gases are continuously injected from one end of the chamber, while by-products and other unreacted substances are continuously removed from the other end using a vacuum pump.

[0003] During evacuation, the plasma entering the exhaust area needs to be quenched to prevent plasma from eroding areas outside the plasma processing zone and to avoid potential radio frequency leakage due to plasma conductivity. Currently, a flow-equalizing ion shield ring is typically placed between the wafer-supporting substrate and the sidewall of the reaction chamber. The ion shield ring has multiple airflow channels penetrating the upper and lower surfaces of the ion shield ring. By adjusting the aspect ratio of the airflow channels, it can be ensured that the plasma gas formed above the substrate is completely extinguished after flowing through the ion shield ring.

[0004] When the confinement ring's gas channels have a high aspect ratio, it can effectively confine the plasma. However, a high aspect ratio in the gas channels leads to a significant reduction in the pumping rate. A lower pumping rate prevents byproducts from being removed in time during the plasma etching process, thus affecting the plasma etching effect.

[0005] How to improve the airflow conduction of the pump while effectively confining the plasma and reducing the risk of plasma leakage is a problem that urgently needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a plasma processing apparatus and a method for preventing plasma leakage. Even when the plasma density in the reaction chamber is high, the airflow conduction of the confinement ring can be improved, and the plasma in the plasma processing area cannot leak through the confinement ring into other areas of the reaction chamber. This effectively solves the problem of easy hole blockage in high aspect ratio etching and can meet the process requirements of rapid switching of process gases in the reaction chamber.

[0007] To achieve the above objectives, the present invention provides a plasma processing apparatus, comprising:

[0008] The reaction chamber contains a base for supporting the wafer; the base is electrically connected to a first non-constant voltage power supply.

[0009] A constraint ring, which surrounds the outer periphery of the base, divides the space within the reaction chamber into a plasma processing area and an exhaust area connected to an external vacuum pumping device; the constraint ring is electrically connected to a second non-constant voltage power supply; the constraint ring prevents plasma from entering the exhaust area.

[0010] Optionally, the plasma processing apparatus further includes: a synchronization control unit electrically connected to a source radio frequency power supply, the source radio frequency power supply being used to generate plasma within the plasma processing area; the synchronization control unit adjusting the output power of the second non-constant voltage power supply based on any one or more of the output power, output frequency, and reflection power of the source radio frequency power supply.

[0011] Optionally, if the output power of the source RF power supply is less than a set power threshold, the output power of the second non-constant voltage power supply is zero; if the output power of the source RF power supply is greater than or equal to the power threshold, the output power of the second non-constant voltage power supply increases as the output power of the source RF power supply increases.

[0012] Optionally, the plasma processing device further includes an optical fiber, a spectral monitoring device, and a synchronization control unit; the optical fiber is used to collect optical signals within the plasma processing area, the spectral monitoring device is used to measure the light intensity of the optical signals, and the synchronization control unit adjusts the output power of the second non-constant voltage power supply based on the change in light intensity.

[0013] Optionally, the plasma processing apparatus further includes a detection device and a synchronization control unit; the detection device is used to detect electrical signals in the exhaust area; the synchronization control unit adjusts the output power of the second non-constant voltage power supply based on the detection results of the detection device.

[0014] Optionally, the first non-constant voltage power supply and the second non-constant voltage power supply are radio frequency power supplies or pulsed DC power supplies; when the second non-constant voltage power supply is a pulsed DC power supply, its output voltage is negative or zero.

[0015] Optionally, the frequency range of the second non-constant voltage is 100Hz to 100MHz.

[0016] Optionally, the amplitude range of the second non-constant voltage power supply is 10V to 10kV.

[0017] Optionally, a plurality of inductively coupled coils are provided above the reaction chamber, and the source radio frequency power supply is applied to the inductively coupled coils.

[0018] Optionally, the plasma treatment apparatus further includes a gas spray head; the gas spray head is disposed above the reaction chamber and opposite the base, for injecting process gas into the plasma treatment area; the source radio frequency power supply is applied to the base or the gas spray head.

[0019] Optionally, the constraint ring is disposed around the inner wall of the base and the reaction chamber; the constraint ring includes a plurality of concentrically arranged ring plates, which are arranged radially along the base.

[0020] Optionally, the constraint ring is disposed between the base and the top wall of the reaction chamber; the constraint ring includes a plurality of concentrically arranged ring plates, which are arranged along the axial direction of the base.

[0021] Optionally, the plasma sheath layer on the surface of the constraint ring can be adjusted to completely fill the gap between adjacent ring plates by adjusting the output power of the second non-constant voltage power supply.

[0022] Optionally, the spacing between adjacent ring plates ranges from 1.5 mm to 5 mm.

[0023] Optionally, the annular plate includes a first surface and a second surface facing each other; the first surface faces the plasma treatment area, and the second surface faces the exhaust area; the distance between the first surface and the second surface ranges from 5 mm to 20 cm.

[0024] Optionally, the surface of the constraint ring is coated with a plating layer resistant to plasma corrosion.

[0025] The present invention also provides a method for preventing plasma leakage, used in a plasma processing apparatus as described in the present invention, comprising the steps of:

[0026] Plasma is generated in the reaction chamber of the plasma processing device by a source radio frequency power supply;

[0027] Based on the output power of the source RF power supply, the output power of the second non-constant voltage power supply applied to the constraint loop is adjusted.

[0028] Optionally, adjusting the output power of the second non-constant voltage power supply includes:

[0029] If the output power of the source RF power supply is less than the set power threshold, the output power of the second non-constant voltage power supply is zero;

[0030] If the output power of the source RF power supply is greater than or equal to the power threshold, the output power of the second non-constant voltage power supply increases as the output power of the source RF power supply increases.

[0031] Optionally, the method for preventing plasma leakage further includes:

[0032] Detect whether plasma leakage occurs in the reaction chamber; if plasma leakage occurs, increase the output power of the second non-constant voltage power supply.

[0033] Optionally, plasma leakage can be detected by measuring the impedance change of the reaction chamber's radio frequency circuit.

[0034] Optionally, changes in light intensity within the reaction chamber can be used to detect whether plasma leakage has occurred.

[0035] Optionally, plasma leakage can be detected by an electrical signal within the exhaust region of the reaction chamber.

[0036] Compared with the prior art, the beneficial effects of the present invention include:

[0037] 1) The plasma processing apparatus and method for preventing plasma leakage of the present invention control the thickness of the plasma sheath layer on the surface of the confinement ring by electrically connecting the confinement ring to a second non-constant voltage power source and controlling the output power of the second non-constant voltage source. For example, increasing the output power of the second non-constant voltage source can effectively increase the potential difference between the confinement ring and the plasma in the plasma processing area, that is, increase the plasma sheath voltage on the surface of the confinement ring, thereby increasing the thickness of the plasma sheath layer on the surface of the confinement ring, so that the plasma sheath layer completely fills the gas flow channel of the confinement ring. When the plasma and reaction byproduct gas pass through the confinement ring, the gas will be smoothly discharged through the gas flow channel, and the electrons and anions in the plasma will bounce off under the action of the plasma sheath layer, avoiding entering the exhaust area. The higher plasma sheath voltage makes it easier for the movement path of the cations in the plasma to be deflected, and the cations are quenched by colliding with the confinement ring. Through the present invention, when the plasma density in the reaction chamber is high, it can also effectively prevent the plasma from leaking through the confinement ring to other areas in the reaction chamber, and ensure that the exhaust gas conduction of the confinement ring meets the process requirements. This invention effectively solves the problems of hole blockage caused by poor venting in high aspect ratio etching while ensuring good plasma confinement. It can also meet the process requirements of rapid switching of process gases in the reaction chamber.

[0038] 2) The synchronous control unit of the present invention can adjust the output power of the second non-constant voltage power supply according to the output power of the source radio frequency power supply. While ensuring that the plasma sheath completely fills the airflow channel of the confinement ring, it can also prevent the plasma sheath voltage from being too high, reduce the bombardment energy of the plasma on the confinement ring, and greatly extend the service life of the confinement ring.

[0039] 3) In this invention, plasma leakage in the reaction chamber can be detected in multiple ways. The synchronous control unit can adjust the output power of the second non-constant voltage power supply based on the detection results, further ensuring that the plasma will not leak to the exhaust area through the constraint ring, effectively preventing the components in the exhaust area and the exhaust pipe connected to the exhaust area from being eroded by the plasma, and preventing the leakage of radio frequency power caused by plasma leakage.

[0040] 4) In this invention, the confinement ring is electrically connected to a second non-constant voltage power supply. Compared with the constant voltage power supply, the second non-constant voltage power supply allows for the formation of a conductive circuit between the plasma in the reaction chamber and the confinement ring through capacitive coupling (without DC conduction) when the surface of the confinement ring is provided with a plasma corrosion resistant coating (insulating material), thereby achieving adjustment of the plasma sheath thickness on the surface of the confinement ring.

[0041] 5) The constraint ring of this invention is composed of multiple ring plates. The constraint ring can be disposed around the inner wall of the base and the reaction chamber, with the multiple ring plates arranged radially along the base. Alternatively, the constraint ring can be disposed between the base and the top wall of the reaction chamber, with the multiple ring plates arranged axially along the base, thereby reducing the volume of the plasma processing area, increasing the plasma density, and improving the efficiency of plasma processing of the wafer. While preventing plasma leakage, compared with the constraint rings of the prior art, the constraint ring of this invention has a wider spacing between adjacent ring plates and a smaller distance between the first and second surfaces of the ring plates, making it easier for airflow to pass between the ring plates and effectively increasing the airflow conduction of the constraint ring. Attached Figure Description

[0042] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the drawings in the following description are one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0043] Figure 1 This is a schematic diagram of a plasma processing device;

[0044] Figure 2 for Figure 1 A schematic diagram of the voltage change between the upper and lower electrodes in a plasma processing device;

[0045] Figure 3 A schematic diagram showing the plasma sheath filling the gas flow channels of the confinement ring to reduce the gas flow conduction of the confinement ring.

[0046] Figure 4 A schematic diagram of plasma leakage occurring in the confinement ring when the airflow conduction of the confinement ring is improved.

[0047] Figure 5 This is a schematic diagram of a plasma processing apparatus in Embodiment 1 of the present invention;

[0048] Figure 6 This is a schematic diagram of the output voltage waveform of the first non-constant voltage power supply in Embodiment 1 of the present invention;

[0049] Figure 7 A schematic diagram of a plasma processing apparatus is shown in another embodiment of the present invention;

[0050] Figure 8 This is a schematic diagram of the plasma sheath filling the gap between adjacent ring plates in Embodiment 1 of the present invention;

[0051] Figure 9 This is a schematic diagram of the plasma processing apparatus in Embodiment 2 of the present invention;

[0052] Figure 10 This is a schematic diagram of the plasma processing apparatus in Embodiment 3 of the present invention;

[0053] Figure 11 This is a schematic diagram of the plasma processing apparatus in Embodiment 4 of the present invention;

[0054] Figure 12 This is a schematic diagram of the plasma processing apparatus in Embodiment 5 of the present invention;

[0055] Figure 13 This is a schematic diagram of a plasma processing apparatus in another embodiment of the present invention;

[0056] Figure 14 This is a flowchart of the method for preventing plasma leakage according to the present invention;

[0057] Figure 15 A flowchart illustrating the adjustment of the output power of the second non-constant voltage power supply in one embodiment of the present invention;

[0058] Figure 16 The flowchart illustrates a method for preventing plasma leakage in another embodiment of the present invention. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0061] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0062] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0063] As used in this specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrases "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0064] Furthermore, in the description of this application, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0065] Figure 1 This is a schematic diagram of a plasma processing device 1. The plasma processing device 1 is a capacitively coupled plasma (CCP) processing device, which includes a vacuum reaction chamber 10, the reaction chamber 10 including a generally cylindrical reaction chamber sidewall 101 made of metallic material.

[0066] A base 102 is disposed at the bottom of the reaction chamber 10 to support the wafer W. A gas spray head 103 is disposed at the top of the reaction chamber 10 and opposite to the base 102. The gas spray head 103 is connected to an external gas supply device 120 via a gas passage to deliver reaction gas into the reaction chamber 10. An exhaust port 130 is disposed at a suitable location in the reaction chamber 10. The exhaust port 130 is connected to an external vacuum device (e.g., a vacuum pump, not shown in the figure) to discharge reaction byproducts from the reaction chamber 10.

[0067] The base 102 serves as the lower electrode of the reaction chamber 10, and the gas spray head 103 serves as the upper electrode of the reaction chamber 10. A radio frequency power supply 140 (e.g., a frequency of 2 MHz to 200 MHz) applies a radio frequency signal to at least one of the upper and lower electrodes. Figure 1 The source radio frequency power supply 140 applies a radio frequency signal to the lower electrode, thereby generating an electric field between the upper and lower electrodes. This electric field accelerates a small number of electrons present inside the reaction chamber 10, causing them to collide with the gas molecules of the input reaction gas. These collisions lead to the ionization of the reaction gas and the excitation of plasma P, thereby generating plasma P within the reaction chamber 10. Plasma P contains a large number of active particles such as electrons, cations, anions, excited-state atoms, molecules, and electrically neutral free radicals.

[0068] Because electrons have a smaller mass than cations, they are more easily accelerated by an electric field, resulting in a greater velocity. Typically, the environment confining the plasma P is grounded, such as the reaction chamber wall. This creates a higher voltage range between the plasma P and the reaction chamber wall, leading to more collisions with the wall due to the faster electron velocity. This generates an electric field near the wall, reducing the number of electrons colliding with it and ensuring that the negative charges (mainly carried by electrons) and positive charges (carried by cations) colliding with the wall are equal in each cycle. Once the electrons and cations stabilize, a plasma sheath forms on the reaction chamber wall. Because the plasma sheath contains almost no electrons, it is also known as a dark region.

[0069] Similarly, such as Figure 2 As shown, a plasma sheath Wa is also formed between the plasma P above wafer W and wafer W. The plasma sheath Wa causes cations to accelerate downwards and bombard the etchable area of ​​wafer W, thereby weakening the intermolecular bonds in the etchable area. The weakened molecular bonds in the etchable area are captured by free radicals, which are converted into volatile gaseous compounds and released, thus forming an etching pattern in the etchable area, completing the etching process. The energy of the cations bombarding wafer W is determined by the voltage (denoted as Vw) of the plasma sheath Wa. Figure 2 As shown, plasma P and plasma sheath Wa have an interface 105. The voltage Vw of plasma sheath Wa refers to the voltage difference between the interface 105 and the wafer W.

[0070] Plasma P has the same potential everywhere. Let the plasma voltage be Vp. Vp is always greater than zero and is always higher than the voltage of a conductor near plasma P. Figures 2 to 4 In the diagram, "○" represents a free radical and "⊕" represents a cation. It represents electrons and anions. Figure 2This diagram illustrates the voltage change between the upper and lower electrodes. As electrons gradually accumulate on the wafer surface, the wafer W is gradually biased to a negative voltage, forming a negative DC bias Vdc on the wafer surface. Vw = Vp - Vdc = Vp + |Vdc|, where |·| represents the absolute value.

[0071] like Figure 1 As shown, the constraint ring 106 (FEIS ring) is electrically grounded and is disposed around the base 102 between the inner wall of the reaction chamber 10, dividing the space inside the reaction chamber 10 into a plasma processing region 10a and an exhaust region 10b. The constraint ring 106 is provided with an airflow channel 1061 connecting the upper and lower surfaces of the constraint ring, for discharging the reaction byproduct gas from the plasma processing region 10a.

[0072] The constraint ring 106 is also used to prevent plasma P from leaking into the exhaust region 10b. The prevention of plasma P leakage as described in this invention refers to preventing the leakage of charged particles (including cations, anions, and electrons) from plasma P.

[0073] During the manufacturing process, a plasma sheath layer 106a is also formed on the surface of the confinement ring 106. To prevent plasma P leakage, such as... Figure 3 As shown, it is necessary to ensure that the plasma sheath 106a completely fills the gas flow channel 1061. When the gas containing plasma P (referred to as plasma gas) flows through the confinement ring 106, the cations in it are deflected by the plasma sheath 106a. Since the confinement ring is grounded, electrons from the ground are transferred to the confinement plate 106 and neutralize the cations hitting the confinement ring 106, thus quenching the cations through collisions with the confinement ring 106. Electrons and anions in the plasma gas are repelled by the plasma sheath 106a and move away from the confinement ring 106, unable to pass through the confinement ring 106. Finally, the plasma gas becomes a neutral gas and flows downwards after flowing through the confinement ring 106.

[0074] like Figure 3 As shown, the plasma sheath 106a and the plasma P have an interface 107. The voltage of the plasma sheath 106a (denoted as Vy) is the voltage difference between the interface 107 and the confinement ring 106. As electrons gradually accumulate on the surface of the confinement ring 106, the confinement ring 106 is gradually biased to a negative voltage, forming a DC bias voltage Vdcy (which is negative) on the surface of the confinement ring 106. Therefore, the voltage of the plasma sheath 106a is Vy = Vp - Vdcy = Vp + |Vdcy|. It is known that the thickness of the plasma sheath 106a is approximately proportional to the cube of the plasma sheath voltage Vy. Usually, Vy is small, resulting in a thinner plasma sheath 106a. Therefore... Figure 3The airflow channel 1061 has a small width d (e.g., less than 1 mm). And... Figure 3 The height h of the airflow channel 1061 (e.g., 10mm-30mm) is also relatively large to ensure that the cations collide with the confinement ring 106. A smaller d and a larger h mean a higher aspect ratio, which will reduce the gas conduction of the confinement ring 106.

[0075] When the suction gas conduction of the constraint ring 106 cannot meet the process requirements, byproducts in the plasma etching process cannot be discharged in time, leading to problems such as deep hole blockage on the surface of the wafer to be etched, thus greatly affecting the plasma etching effect. Furthermore, the low suction gas conduction cannot meet the requirements of some etching processes that require rapid switching of process gases within a short time. For example, in the ALE (Atomic Layer Etching) process, the original process gas in the reaction chamber 10 needs to be rapidly removed and a new process gas injected within a time frame of 0.1 to 0.5 seconds.

[0076] Figure 4 In order to ensure that the airflow conduction of the confinement ring 106 meets the process requirements, the width d of the airflow channel 1061 is increased (e.g., 1mm to 2mm). This will cause the plasma sheath layer 106a to not completely fill the airflow channel 1061. Especially when the output power of the source RF power supply 140 increases, the plasma density in the reaction cavity 10 increases, and electrons, anions, and cations can easily pass through the confinement ring 106, resulting in plasma P leakage. This not only contaminates the inner wall of the reaction cavity and the exhaust pipe below the confinement ring 106, but also causes the RF energy in the reaction cavity 10 to leak to the outside of the reaction cavity 10 through the plasma P in the exhaust region 10b, affecting the safety of wafer processing.

[0077] This invention provides a plasma processing apparatus and a method for preventing plasma leakage. Even when the plasma density in the reaction chamber is high, it can improve the gas flow conduction of the confinement ring and prevent plasma leakage. This invention effectively solves the problem of easy via clogging in high aspect ratio etching and can meet the process requirements of rapid switching of process gases within the reaction chamber.

[0078] Example 1

[0079] Figure 5 This is a schematic diagram of the plasma processing device 2 in Embodiment 1 of the present invention. It is a capacitively coupled plasma processing device, including a reaction chamber 20. The reaction chamber 20 is provided with a base 202 for supporting the wafer W, a gas spray head 203, and a constraint ring 206.

[0080] A gas spray head 203 is positioned above the reaction chamber 20 and opposite the base 202, for injecting process gas into the reaction chamber 20. The gas spray head 203 and the base 202 serve as the upper and lower electrodes of the reaction chamber 20, respectively. A source radio frequency power supply 240 is applied to the base 202 or the gas spray head 203 to generate plasma P (the voltage of plasma P is denoted as Vp) within the reaction chamber 20. Figure 5 As shown, in this embodiment, the source RF power supply 240 is applied to the base 202, and the gas spray head 203 is grounded. During the process, electrons gradually accumulate on the wafer surface, and the wafer W is gradually biased to a negative voltage, forming a DC bias voltage Vdc on the wafer surface. ′ (Vdc ′ (less than zero).

[0081] like Figure 5 As shown, the base 202 is also electrically connected to a first non-constant voltage power supply 241 (whose output voltage is denoted as V1). The first non-constant voltage power supply 241 in this invention is an radio frequency (RF) power supply or a pulsed DC power supply, and its RF power can be transmitted to the base 202 via capacitive coupling. The voltage of the plasma sheath layer on the wafer surface is denoted as Vw. ′ Under the action of the first non-constant voltage power supply 241, Vw ′ =Vp-Vdc ′ -V1, where |Vdc ′ |Proportional to the magnitude of V1.

[0082] like Figure 6 As shown, when the first non-constant voltage power supply 241 is an RF power supply, the wafer surface voltage is positive for only a brief period during its entire operating cycle T, during which electrons in plasma P flow into the lower electrode. When V1 is negative, cations in plasma P flow into the lower electrode almost continuously. In a steady state, the total amount of charge flowing into the lower electrode in each operating cycle T is zero. When V1 is positive, Vw ′ =Vp+|Vdc ′ |-|V1|. When V1 is negative, Vw ′ =Vp+|Vdc ′ |+|V1|. For most of the working cycle T, Vw is at a high voltage. Compared to when the first non-constant voltage power supply 241 is not applied, the plasma sheath voltage Vw generally increases, thus increasing the energy of cations bombarding the wafer W. Vw can be adjusted by regulating V1 (i.e., adjusting the output power of the first non-constant voltage power supply 241), thereby regulating the energy of cations bombarding the wafer surface.

[0083] When the first non-constant voltage power supply 241 is a pulsed DC power supply, its output voltage is negative or zero. When the output voltage V1 of the first non-constant voltage power supply 241 is negative, Vw ′=Vp+|Vdc ′ |+|V1|. When the output voltage of the first non-constant voltage power supply 241 is zero, Vw ′ =Vp+|Vdc ′ The larger the duty cycle and the higher the output power (|V1|) of the first non-constant voltage power supply 241, the greater the energy of the cations bombarding the wafer surface.

[0084] like Figure 5 As shown, a constraint ring 206 is disposed between the base 202 and the inner wall of the reaction chamber 20, dividing the space within the reaction chamber 20 into a plasma processing area 20a and an exhaust area 20b connected to an external vacuum pump (not shown in the figure). The constraint ring 206 prevents plasma P from entering the exhaust area 20b. In this invention, a plasma P-resistant coating is provided on the surface of the constraint ring 206, and the coating is made of an insulating material (e.g., alumina, yttrium oxide, etc.).

[0085] like Figure 5 As shown, the constraint ring 206 in this embodiment includes a plurality of concentrically arranged ring plates 2062, which are arranged radially along the base 202. The gap between two adjacent ring plates 2062 forms an airflow channel 2061, through which reaction byproducts in the plasma processing region 20a flow into the exhaust region 20b.

[0086] In another embodiment, such as Figure 7 As shown, the constraint ring 206 is disposed between the base 202 and the top wall of the reaction chamber 20, and the multiple ring plates 2062 of the constraint ring 206 are arranged along the axial direction of the base 202. This can reduce the volume of the plasma processing region 20a, increase the plasma density in the plasma processing region 20a, and improve the efficiency of plasma processing of the wafer W.

[0087] like Figure 5 , Figure 7 As shown, the constraint ring 206 is electrically connected to the second non-constant voltage power supply 210. The second non-constant voltage power supply 210 can be an radio frequency power supply or a pulsed DC power supply. When the second non-constant voltage power supply 210 is a pulsed DC power supply, its output voltage is negative or zero. In this embodiment, the frequency range of the second non-constant voltage power supply 210 is 100Hz to 100MHz, and the amplitude range is 10V to 10kV.

[0088] The plasma P above the confinement ring 206 and the confinement ring 206 can be understood as the two plates of a capacitor, and the coating on the surface of the confinement ring 206 can be understood as the dielectric of the capacitor. A conductive circuit is formed between the plasma P and the confinement ring 206 through capacitive coupling.

[0089] As electrons gradually accumulate on the surface of the constraint ring 206, the constraint ring 206 is gradually biased to a negative voltage, forming a DC bias voltage Vdcy on the surface of the constraint ring 206. ′ (It is a negative value). The voltage of the plasma sheath 206a is denoted as Vy. ′ The output voltage of the second non-constant voltage power supply 210 is denoted as V2. Under the action of the second non-constant voltage power supply 210, Vy ′ =Vp-Vdcy ′ -V2, where |Vdcy ′ | is proportional to the magnitude of V2.

[0090] When the second non-constant voltage power supply 210 is an RF power supply:

[0091] When V2 is negative, Vy ′ =Vp+|Vdcy ′ |+|V2|. By adjusting the output power of the second non-constant voltage power supply 210 (i.e., adjusting the amplitude of V2), Vdcy can be effectively changed. ′ This allows for the regulation of the voltage Vy in the plasma sheath 206a. ′ The thickness of the plasma sheath 206a is approximately proportional to the plasma sheath voltage Vy. ′ The thickness of the plasma sheath 206a on the surface of the constraint ring 206 can be adjusted by regulating the output power of the second non-constant voltage power supply 210, so that the plasma sheath 206a completely fills the gap between adjacent ring plates 2062 (e.g., the third power of the fourth power). Figure 8 (As shown), to prevent plasma P leakage.

[0092] When V2 is positive, Vy ′ =Vp+|Vdcy ′ |-|V2|. By adjusting the output power of the second non-constant voltage power supply 210 (that is, adjusting the amplitude of V2), |Vdcy can be adjusted. ′ | Large enough that Vy is positive for most of the time. ′ It is also large enough to ensure that the plasma sheath 206a completely fills the gap between adjacent annular plates 2062. On the other hand, since the collapse of the plasma sheath 206a requires a long time, during the short period when V2 is positive, even if Vy ′ The plasma sheath 206a is relatively small and will not collapse, thus preventing plasma P leakage.

[0093] For example, Figure 4 The DC bias voltage on the surface of the confinement ring 106 is approximately -100V, the voltage Vp of plasma P is approximately 20V, and the voltage Vy of the plasma sheath 106a is approximately 120V. However, to ensure that the plasma sheath 106a fills the gas flow channel 1061, Vy needs to reach 200V. Therefore... Figure 4 Plasma leakage will occur in the confinement ring 106. Figure 8 constraint loop 206 and Figure 4 The constraint ring 106 has the same morphology. The second non-constant voltage power supply 210 is an radio frequency power supply, and its output voltage V2 fluctuates in the range of -1000V to 1000V. ′ If the voltage is approximately -1000V and Vp is approximately 20V, then the voltage Vy of the plasma sheath 206a is... ′ The fluctuation range is approximately 20V to 2020V. For most of the operating cycle of the second non-constant voltage power supply 210, Vy... ′ A voltage greater than or equal to 200V can effectively increase the thickness of the plasma sheath 206, preventing plasma P from leaking from the gaps between adjacent ring plates 2062. During a very short period (e.g., 0.01 seconds) of the second non-constant voltage power supply 210's operating cycle, Vy... ′ Below 200V, due to the long collapse time (e.g., 0.5 seconds) required for the plasma sheath 206a, the voltage drop at Vy is significant. ′ There is no risk of plasma P leakage even at voltages below 200V. It should be noted that the above values ​​are merely examples and are not intended to limit the scope of this invention.

[0094] When the second non-constant voltage power supply 210 is a pulsed DC power supply:

[0095] When the output voltage V2 of the second non-constant voltage power supply 210 is negative, Vy ′ =Vp+|Vdcy ′ |+|V2|. When the output voltage of the second non-constant voltage power supply 241 is zero, Vy ′ =Vp+|Vdcy ′ | By adjusting the output power of the second non-constant voltage power supply 210 (i.e., adjusting the amplitude of V2), |Vdcy can be effectively adjusted. ′ |, thereby adjusting the voltage Vy of the plasma sheath 206a. ′ This ensures that the plasma sheath 206a fills the gap between adjacent 2062.

[0096] like Figure 5 , Figure 7As shown, the ring plate 2062 includes a first surface 2063 and a second surface 2064 facing each other. The first surface 2063 faces the plasma processing region 20a, and the second surface 2064 faces the exhaust region 20b. The constraint ring 206 of the present invention effectively prevents plasma P leakage, while the spacing between adjacent ring plates 2062 can be increased to 1.5 mm to 5 mm (greater than the aforementioned width d), and the distance between the first surface 2063 and the second surface 2064 can be reduced to 5 mm to 20 mm (less than the aforementioned height h). Therefore, compared with the constraint ring 106, the constraint ring 206 of the present invention has higher pumping conductivity.

[0097] In summary, this invention significantly improves the confinement effect of the confinement ring 206 on the plasma P, effectively preventing plasma P from leaking through the confinement ring 206 to the exhaust region 20b even when the plasma density in the reaction chamber 20 is high. This invention also improves the gas flow conduction of the confinement ring 206, effectively solving the problem of easy hole clogging in high aspect ratio etching, and meeting the process requirements for rapid switching of process gases within the reaction chamber 20.

[0098] Example 2

[0099] Due to the plasma sheath voltage Vy ′ The higher the concentration of cations, the greater the bombardment force of the cations on the confinement ring 206, and the easier it is to damage the confinement ring 206. For example... Figure 9 As shown, the plasma processing device 2 in this embodiment also includes a synchronization control unit 220, which is electrically connected to the source radio frequency power supply 240. The synchronization control unit 220 adjusts the output power of the second non-constant voltage power supply 210 based on the output power of the source radio frequency power supply 240, ensuring that the plasma sheath 206a completely fills the gaps between the annular plates 2062 while preventing the plasma sheath voltage Vy from increasing. ′ Excessive energy reduces the bombardment energy of cations on confinement ring 206, greatly extending the service life of confinement ring 206.

[0100] The working principle of the synchronization control unit 220 is as follows:

[0101] The plasma density in the plasma processing region 20a increases with the increase of the output power of the source radio frequency power supply 240, while the thickness of the plasma sheath 206a decreases with the increase of the plasma density.

[0102] When the output power of the source RF power supply 240 is low, the plasma density in the reaction chamber 20 is low, and the plasma sheath 206a is thick. The second non-constant voltage power supply 210 only needs to output a small power (small V2) or zero power (V2 equals 0) to obtain the required plasma sheath voltage Vy. ′This ensures that the plasma sheath 206a fills the gap between adjacent ring plates 2062 while also preventing excessive bombardment energy from being provided to the cations, thus extending the service life of the confinement ring 206.

[0103] When the output power of the source RF power supply 240 is high, the plasma density inside the reaction chamber 20 is high, and the plasma sheath 206a on the surface of the confinement ring 206 is thin. The second non-constant voltage power supply 210 needs to output a larger power (V2 is higher) to obtain a larger plasma sheath voltage Vy. ′ This increases the thickness of the plasma sheath 206a, preventing plasma P leakage.

[0104] In this embodiment, when the output power of the source RF power supply 240 is less than a set power threshold, the output power of the second non-constant voltage power supply 210 is zero. If the output power of the source RF power supply 240 is greater than or equal to the power threshold, the output power of the second non-constant voltage power supply 210 increases as the output power of the source RF power supply 240 increases.

[0105] Example 3

[0106] In this embodiment, the synchronization control unit 220 detects whether plasma P leakage occurs in the reaction cavity 20 based on the impedance change of the reaction cavity radio frequency circuit. If plasma P leakage occurs, the output power of the second non-constant voltage power supply 210 is increased.

[0107] In this embodiment, as Figure 10 As shown, the RF impedance matching device 243 is electrically connected between the source RF power supply 240 and the lower electrode. The RF impedance matching device 243 ensures that the source RF power supply 240 and the reaction chamber 20 are in an impedance-matched state, thereby maximizing the coupling of the RF power of the source RF power supply 240 to the lower electrode.

[0108] When plasma P leaks, the impedance of the reaction cavity 20 also changes, which will lead to an increase in the reflected power of the source RF power supply 240 and a decrease in the RF power supplied by the source RF power supply 240 to the reaction cavity 20 (used to generate plasma P). If the reflected power is too high, it can also easily cause a short circuit or open circuit in the RF circuit of the reaction cavity, thereby causing the wafer W to be scrapped.

[0109] In this embodiment, the synchronization control unit 220 measures the reflected power of the source radio frequency power supply 240. If the reflected power exceeds the set threshold, it is determined that plasma P leakage has occurred in the reaction chamber 20, and the synchronization control unit 220 drives the second non-constant voltage power supply 210 to increase the output power.

[0110] In another embodiment, the output frequency of the source RF power supply 240 can be automatically adjusted. When plasma P leakage occurs, the source RF power supply 240 adjusts its own impedance by changing its output frequency to match the impedance change of the reaction cavity 20, thereby making the reflected power zero. The synchronization control unit 220 measures whether the output frequency of the source RF power supply 240 changes. If it changes, it determines that plasma P leakage has occurred in the reaction cavity 20, and the synchronization control unit 220 drives the second non-constant voltage power supply 210 to increase its output power.

[0111] Example 4

[0112] In this embodiment, as Figure 11 As shown, it also includes an optical fiber 251 and a spectral monitoring device 252. The optical fiber 251 passes through the wall of the reaction chamber and is used to collect the optical signal within the plasma processing region 20a (the plasma processing region 20a contains electrons, so it emits light), and the spectral monitoring device 252 is used to measure the light intensity of the optical signal.

[0113] The synchronization control unit 220 determines whether plasma P leakage has occurred in the reaction chamber 20 based on the light intensity measured by the spectral monitoring device 252. If no plasma P leakage has occurred, the light intensity measured by the spectral monitoring device 252 remains unchanged. Otherwise, if the light intensity measured by the spectral monitoring device 252 changes, the synchronization control unit 220 drives the second non-constant voltage power supply 210 to increase its output power.

[0114] Example 5

[0115] like Figure 12 As shown, a detection device 260 is provided within the exhaust region 20b to detect electrical signals within the exhaust region 20b. In a preferred embodiment, the detection device 260 is located near the second surface of the constraint ring 206. When plasma P leakage occurs, charged particles in plasma P will pass through the gaps between the ring plates 2062 and enter the exhaust region 20b. Therefore, when the detection device 260 detects an electrical signal, it indicates that plasma P leakage has occurred; otherwise, it is considered that no plasma P leakage has occurred.

[0116] Based on the detection results from the detection device 260, the synchronization control unit 220 adjusts the output power of the second non-constant voltage power supply 210. In this embodiment, if the detection device 260 detects an electrical signal, the synchronization control unit 220 drives the second non-constant voltage power supply 210 to increase its output power.

[0117] In summary, the present invention can detect plasma P leakage in the reaction chamber 20 in multiple ways, and adjust the output power of the second non-constant voltage power supply 210 based on the detection results to further ensure that plasma P leakage does not occur, effectively prevent the components in the exhaust region 20b and the exhaust pipe connected to the exhaust region 20b from being eroded by plasma P, and prevent the leakage of radio frequency power caused by plasma P leakage.

[0118] In other embodiments, the plasma processing apparatus 3 of the present invention can also be an inductively coupled plasma (ICP) processing apparatus, such as... Figure 13 As shown, it includes: a reaction chamber 30, a liner 305, an insulating window 303, multiple inductively coupled coils 308, a base 302, a constraint ring 306, and a synchronization control unit 320.

[0119] The reaction chamber 30 includes a generally cylindrical reaction chamber sidewall 301 made of metallic material. An insulating window 303 is located at the top of the reaction chamber 30, and a reaction gas injection port 307 is provided at one end of the reaction chamber sidewall 301 near the insulating window 303. An inductively coupled coil 308 is located above the insulating window 303 and is electrically connected to a source radio frequency power supply 340. Under the excitation of the source radio frequency power supply 340, the inductively coupled coil 308 generates an induced magnetic field, and the reaction gas in the reaction chamber 30 generates plasma P under the action of the induced magnetic field. A liner 305 is disposed inside the reaction chamber 30 to protect the inner wall of the reaction chamber 30 from corrosion by the plasma P.

[0120] The base 302 is located at the bottom of the reaction chamber 30 and is used to support the wafer W. The base 302 is also electrically connected to the first non-constant voltage source 341, which controls the bombardment direction of cations in the plasma P.

[0121] A confinement ring 306 is disposed between the base 302 and the sidewall 301 of the reaction chamber. The confinement ring 306 is electrically connected to a second non-constant voltage power supply 310, which outputs a negative voltage or zero voltage. The synchronization control unit 320 adjusts the output power of the second non-constant voltage power supply 310 based on the output power of the source radio frequency power supply 340. This prevents plasma P leakage while reducing the bombardment energy of cations on the confinement ring 306, greatly extending the service life of the confinement ring 306.

[0122] The present invention also provides a method for preventing plasma leakage, used in a plasma processing apparatus as described in the present invention, such as... Figure 14 As shown, the steps include:

[0123] S100. Plasma is generated in the reaction chamber of the plasma processing device by a source radio frequency power supply;

[0124] S200: Based on the output power of the source RF power supply, adjust the output power of the second non-constant voltage power supply applied to the constraint loop.

[0125] In one embodiment, such as Figure 15 As shown, adjusting the output power of the second non-constant voltage power supply in step S200 includes:

[0126] S201. If the output power of the source RF power supply is less than the set power threshold, the output power of the second non-constant voltage power supply is zero.

[0127] S202. If the output power of the source RF power supply is greater than or equal to the power threshold, the output power of the second non-constant voltage power supply increases as the output power of the source RF power supply increases.

[0128] In another embodiment, such as Figure 16 As shown, the method for preventing plasma leakage further includes the following steps:

[0129] S300: Detect whether plasma leakage occurs in the reaction chamber; if plasma leakage occurs, increase the output power of the second non-constant voltage power supply.

[0130] For the plasma processing device in Embodiment 3, whether plasma leakage occurs can be detected by the impedance change of the radio frequency circuit of the reaction chamber.

[0131] For the plasma processing device in Embodiment 4, whether plasma leakage has occurred can be detected by the change in light intensity within the reaction chamber.

[0132] For the plasma processing device in Embodiment 5, whether plasma leakage has occurred can be detected by the electrical signal in the exhaust area of ​​the reaction chamber.

[0133] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0134] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A plasma processing device, characterized in that, include: The reaction chamber contains a base for supporting the wafer; The base is electrically connected to a first non-constant voltage power supply; A constraint ring, which surrounds the outer periphery of the base, divides the space within the reaction chamber into a plasma processing area and an exhaust area connected to an external vacuum pumping device; the constraint ring is electrically connected to a second non-constant voltage power supply; the constraint ring prevents plasma from entering the exhaust area.

2. The plasma processing apparatus as described in claim 1, characterized in that, Also includes: A synchronization control unit is electrically connected to a source radio frequency power supply, which is used to generate plasma within the plasma processing area; The synchronization control unit adjusts the output power of the second non-constant voltage power supply based on any one or more of the output power, output frequency, and reflected power of the source radio frequency power supply.

3. The plasma processing apparatus as described in claim 2, characterized in that, If the output power of the source RF power supply is less than the set power threshold, the output power of the second non-constant voltage power supply is zero; if the output power of the source RF power supply is greater than or equal to the power threshold, the output power of the second non-constant voltage power supply increases as the output power of the source RF power supply increases.

4. The plasma processing apparatus as described in claim 1, characterized in that, It also includes optical fibers, spectral monitoring equipment, and a synchronization control unit; the optical fibers are used to collect optical signals within the plasma processing area, and the spectral monitoring equipment is used to measure the intensity of the optical signals. The synchronization control unit adjusts the output power of the second non-constant voltage power supply based on the change in light intensity.

5. The plasma processing apparatus as described in claim 1, characterized in that, It also includes a detection device and a synchronization control unit; the detection device is used to detect electrical signals in the exhaust area; the synchronization control unit adjusts the output power of the second non-constant voltage power supply based on the detection results of the detection device.

6. The plasma processing apparatus as described in claim 1, characterized in that, The first non-constant voltage power supply and the second non-constant voltage power supply are radio frequency power supplies or pulsed DC power supplies; when the second non-constant voltage power supply is a pulsed DC power supply, its output voltage is negative or zero.

7. The plasma processing apparatus as described in claim 6, characterized in that, The frequency range of the second non-constant voltage is 100Hz to 100MHz.

8. The plasma processing apparatus as described in claim 6, characterized in that, The amplitude range of the second non-constant voltage power supply is 10V to 10kV.

9. The plasma processing apparatus as described in claim 2, characterized in that, Multiple inductively coupled coils are provided above the reaction chamber, and the source radio frequency power supply is applied to the inductively coupled coils.

10. The plasma processing apparatus as described in claim 2, characterized in that, It also includes a gas spray head; the gas spray head is disposed above the reaction chamber and opposite the base, for injecting process gas into the plasma processing area; the source radio frequency power supply is applied to the base or the gas spray head.

11. The plasma processing apparatus as claimed in claim 1, characterized in that, The constraint ring is disposed between the base and the inner wall of the reaction chamber; the constraint ring includes a plurality of concentric ring plates arranged radially along the base.

12. The plasma processing apparatus as claimed in claim 1, characterized in that, The constraint ring is disposed between the base and the top wall of the reaction chamber; the constraint ring includes a plurality of concentrically arranged ring plates, which are arranged along the axial direction of the base.

13. The plasma processing apparatus as described in any one of claims 11 or 12, characterized in that, By adjusting the output power of the second non-constant voltage power supply, the plasma sheath layer on the surface of the constraint ring can completely fill the gap between the adjacent ring plates.

14. The plasma processing apparatus as described in any one of claims 11 or 12, characterized in that, The spacing between adjacent ring plates ranges from 1.5 mm to 5 mm.

15. The plasma processing apparatus as described in any one of claims 11 or 12, characterized in that, The ring plate includes a first surface and a second surface facing each other; the first surface faces the plasma treatment area, and the second surface faces the exhaust area; the distance between the first surface and the second surface ranges from 5 mm to 20 cm.

16. The plasma processing apparatus as claimed in claim 1, characterized in that, The surface of the constraint ring is coated with a plating layer resistant to plasma corrosion.

17. A method for preventing plasma leakage, used in a plasma processing apparatus as described in any one of claims 1 to 16, characterized in that, Including the following steps: Plasma is generated in the reaction chamber of the plasma processing device by a source radio frequency power supply; Based on the output power of the source RF power supply, the output power of the second non-constant voltage power supply applied to the constraint loop is adjusted.

18. The method for preventing plasma leakage as described in claim 17, characterized in that, Adjusting the output power of the second non-constant voltage power supply includes: If the output power of the source RF power supply is less than the set power threshold, the output power of the second non-constant voltage power supply is zero; If the output power of the source RF power supply is greater than or equal to the power threshold, the output power of the second non-constant voltage power supply increases as the output power of the source RF power supply increases.

19. The method for preventing plasma leakage as described in claim 17, characterized in that, Also includes: Detect whether plasma leakage has occurred within the reaction chamber; If plasma leakage occurs, increase the output power of the second non-constant voltage power supply.

20. The method for preventing plasma leakage as described in claim 19, characterized in that, Whether plasma leakage has occurred is detected by the impedance change of the radio frequency circuit of the reaction chamber.

21. The method for preventing plasma leakage as described in claim 19, characterized in that, Whether plasma leakage has occurred is detected by changes in light intensity within the reaction chamber.

22. The method for preventing plasma leakage as described in claim 19, characterized in that, Whether plasma leakage has occurred is detected by an electrical signal in the exhaust area of ​​the reaction chamber.

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